Hi Jarrid,
the later over drives had the balance tube cast into the tailhousing,
you can see it as a ridge running from back to front. The one on EBay is
this later type and is for series 5 but will fit all Alpines with a 10
spline shaft. I think the cut over from the external return pipe was
around early series 2.
I have seen a couple of different versions of the external pipe
The difference in the gearbox adapter is as you say, to cover and extra
oil hole in the rear face of the gearbox.
It is a fairly crude addition of a semi-circular lug which extends out
to block off the hole on the upper rear face of the gearbox.
regards
Jeff
In message <3AAB24AE.869A1FFE@earthlink.net>, Jarrid Gross
<jarrid_gross@earthlink.net> writes
>TIGEROOTES@aol.com wrote:
>
>> Jarrid,
>> What is the difference between the early and late overdrive adapters
>> ("doughnut spacers")? You said there is an additional oil passageway. I
>> have seen many units with an outboard copper tube plumbed across the spacer,
>> and I believe it was a factory update. Is this the equivalent of the oil
>> passageway?
>> Jim
>
>The overdrive adapters are about 4 inch extensions of where the
>tailcase would have been mounted on standard transmisions.
>Early and late look almost identical, except that late ones have
>a 3/8 or so extra drain hole towards the bottom, which appears
>to let tailcase oil drain back into the gearbox, perhaps fixing
>a design flaw with the early tranmisions (who knows).
>The gaskets between the gearbox and the apapter/tailcase tell the
>whole story. Get one of each and compare.
>
>There had been problems with some sort of a pressure buildup in the OD
>unit, which somehow blew the gearbox oil out the tail section of the OD.
>I dont think the add on tube was a functional equiv to the later
>oil return as the od adapter has no seal in it, and therfore
>wouldnt contribute to a pressure buildup in the OD.
>
>The fix was to put a balance pipe "probably what you have seen"
>escentially across the overdrive unit.
>Seemingly dumping any pressure buildup back to the gearbox,
>or nulling out a pressure differential.
>
>The funny thing is that although it was afcatory fix, most later ODs
>dont seem to have the modification.
>
>Not sure under what circumstances the oil departed, or if there was
>a more appropriate internal fix, but the fact remains that many if
>not most survining ODs dont have the fix.
>
>The rebuilt OD trans on ebay doesnt seem to have the balance tube,
>and its an all-sync.
>
>Anyone know why Rootes stopped the pressure hose mod?
>
>Seems to be a rootes only problem as the other laycock
>overdrives that used the flange type output didnt seem to have
>this mod.
>
>Jarrid Gross
--
Jeff Howarth
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